Guess you missed the point of what is happening with Course and Training.
You do NOT use $Course for parsing the TrainingEvent title.
This is related to this topic Associations https://academy.mendix.com/link/modules/82/lectures/635/4.8-Associations-in-the-Domain-Model
In the microflow ACT_Course_ScheduleTrainingEvent a new TrainingEvent object is created with a reference to the Course object. Association is Mendix are defined using the Object ID's which are created and maintained by the Mendix runtime. You won't create your own foreign keys. Which need to be explicitly set when setting the association between two objects. Thus simply refering to an object is sufficient to set the association, because Mendix will pick the object ID automatically.